The present invention relates to a high frequency generating device and, more particularly, to a filter devices for a high frequency generating device.
High frequency generating devices such as, for example, magnetron, klystron, traveling-wave tube and semiconductor device, have found their various uses. The high frequency generating device is frequently provided with a filter device for restricting undesirable leaks of high frequency energy. The leaks of high frequencies become the cause of noise in radio and TV receivers or other electronic apparatuses. For this, the filter device for restricting such high frequency leaks is very important in the high frequency generating devices. The filter device generally comprises inductance elements such as choke elements, capacitors and a shield box and is generally connected to the power supply conductors. The improvement of the filter circuit is disclosed in U.S. Patent No. 3,922,612 issued on Nov. 25, 1975 and assigned to the assignee of the present application. For the choke element of the filter circuit, a core type inductor is usually used, which is small in size and high in performance. As described in the above-mentioned patent, the core type inductor is a choke element of a combination of a coil and a member having a large high frequency loss and high magnetic permeability such as ferrite. Since ferrite or material including mainly ferrite has high magnetic permeability and good high frequency absorptive characteristic, the core type inductor serves as an inductance element to the high frequency components within a frequency range and exhibits its good high frequency absorptive nature for other high frequency components to damp them. However, the core type inductor is frequently heated to an extremely high temperature, thereby resulting possibly in burning of the core, i.e. the ferrite. This arises from the fact that, when the high frequency energy through the power supply conductors is extremely high, the core absorbes most of the high frequency energy, and that the core is disposed at the high electromagnetic field of the standing wave developed in the power supply conductors.